This invention relates to clutches in general and, in particular, to a new and useful rotation-elastic, shock and vibration damping clutch in which two clutch rings are connected by a rubber-elastic pressure pad of arc-shaped cross-section and by at least one rope strand of a non-elastic connecting rope which is evenly distributed over the circumference of the clutch and connected to the pressure pad.
One of the two clutch rings, usually the inner one, is connected to the driving shaft of a machine and the other, usually the outer clutch ring, is connected to the shaft to be driven. The job of the connecting ropes, or their rope strands, is to transmit the torque from the one clutch ring to the other, while the rubber-elastic pressure pad supports the rope strands, particularly influencing the rotation elasticity and the vibration damping of the clutch.
A clutch of this kind is known from German Pat. No. 23 18 612, in which the pressure pad comprises an elastic shell filled with a pressure medium, with non-elastic plastic ropes being led around the pressure pad or embedded in it. Among others, this clutch has the disadvantage that its rotation elasticity depends to a considerable extent on the pressure of the pressure medium filling the pressure pad. Apart from unpreventable leakage losses, the internal pressure of the pressure pad changes in the course of operation due to temperature fluctuations to which the clutch is subjected, so that the rotation elasticity of the clutch is also subject to considerable variations.
Another clutch of this kind is known from German Pat. No. 26 26 414. It differs in essence from the above-mentioned clutch in that the pressure pad is not filled with a pressure medium, but instead consists of a rubber part of stable shape with a jacket-shaped annular space open towards one side in the axial direction.
The two above-mentioned clutches have, in common, that the elasticity of the clutch is essentially determined by the elasticity of the pressure pad while the ropes, led through openings in the clutch rings connected by the pressure pad and fixed in the clutch rings, contribute to the shock and vibration attenuation of the clutch merely by the rope strands being supported by the arched pressure pad. If only for reasons of design, the result is a considerable flexural stiffness of the clutch rings because their fastening to the shafts to be connected by the clutch requires certain minimum dimensions which, in the outer ring for instance, are determined essentially by the number of, and diameter of, the connecting screws required, and by the openings required for the connecting ropes.
For example, the ratio of the outer clutch ring stiffness to the stiffness of the rope strands is about 10,000:1 in such clutches. It, therefore, follows that differences in the length of the rope strands automatically result in their also being stressed differently. Since the connecting ropes or rope strands contact the walls and edges of the openings through which they are led, they are bent sharply at the hole edges when the clutch is stressed by shocks and torque variations and are easily damaged due to the notch effect occurring thereby.
In German Pat. No. 26 57 527, a rotation-elastic clutch is suggested in which the last-named disadvantage is avoided by providing that the openings in which the connecting ropes are fastened to the clutch rings are provided with bushings or coatings, in particular, plastic bushings or coatings. These bushings or coatings are to have the effect of enabling the ropes or rope strands to glide in the openings without much friction so as to avoid edge contusions. It has turned out, however, that rope damage, due to severe rope bending at the hole edges cannot be eliminated by these known measures, and that rope breakage due to the notch effect at the hole edges still occurs at great torque variations.